Method for metallizing a non-metallic substrate and pre-treatment composition

ABSTRACT

The present invention relates to a method for metallizing a non-metallic substrate, the method comprising the steps (A) to (C), wherein step (A) is a pre-treatment step for etching and step (C) the metallization step. In step (A) a pre-treatment composition is utilized comprising individual manganese (II), (III), and (IV) species. The present invention furthermore relates to a specific pre-treatment composition.

FIELD OF THE INVENTION

The present invention relates to a method for metallizing a non-metallicsubstrate, the method comprising the steps (A) to (C), wherein step (A)is a pre-treatment step for etching and step (C) the metallization step.In step (A) a pre-treatment composition is utilized comprisingindividual manganese (II), (III), and (IV) species. The presentinvention furthermore relates to a specific pre-treatment composition.

BACKGROUND OF THE INVENTION

Metallizing non-metallic substrates such as plastic substrates has along history in modern technology. Typical applications are found inautomotive industry as well as for sanitary articles.

However, making a non-metallic/non-conductive substrate receptive for ametal layer is demanding. Typically, a respective method starts with asurface modification of the substrate's surface, typically known asetching. Usually, a sensitive balance is required in order to ensure asufficient surface roughening without causing too strong defects.

Many methods and etching compositions are known, including compositionscomprising environmentally questionable chromium species, such ashexavalent chromium species. Although these compositions usually providevery strong and acceptable etching results, environmentally friendlyalternatives are more and more demanded and to a certain extent alreadyprovided in the art.

For example, WO 2018/095998 A1 refers to a chrome free etch for platingon plastic processes, wherein plastic surfaces are contacted in a firststep with an etching solution at least comprising Mn(IV)-ions and, in asecond etching step, with a solution at least comprising Mn(III)- andMn(VII)-ions prior to the plating step.

EP 3 584 352 A1 refers to a pretreatment composition for electrolessplating and a respective pretreatment method exhibiting high platingdeposition performance without using harmful chromic acid and expensivepalladium, while reducing the number of steps.

EP 0 913 498 A1 refers to a process combining surface treatment andmetal deposition. A respective aqueous solution comprises a metalactivator, such as an oxidized species of silver, cobalt, ruthenium,cerium, iron, manganese, nickel, rhodium, or vanadium. The activator canbe suitably oxidized to a higher oxidation state electrochemically.

EP 2 025 708 A1 refers to an etching solution comprising Mn(VII) ions.

EP 2 937 446 B1 refers to a composition for etching treatment of a resinmaterial, the composition comprising permanganate ions.

US 2017/159183 A1 refers to a resin plating method using an etching bathcontaining manganese as an active ingredient.

U.S. Pat. No. 8,603,352 B1 refers to a chrome-free composition of anacidic suspension of manganese compounds and manganese ions are appliedto an organic polymer surface to etch the surface. The suspensioncomprises one or more undissolved Mn(II) compounds, or one or moreundissolved Mn(III) compounds, or mixtures thereof, dissolved Mn(II)ions and dissolved Mn(III) ions, and one or more acids.

CN 110172684 A refers to the formulation and preparation of achromium-free roughening solution for ABS plastics.

As seen above, in many cases, manganese species are utilized instead ofchromium ions. However, certain manganese species inherently havespecific disadvantages. For example, manganese (VII) species typicallyform difficult to handle manganese dioxide, which often adsorbs on thesurface of the substrate and needs to be chemically reduced in order todissolve it.

Furthermore, besides the issue of environmentally questionable chromiumions, the etching process additionally affects the overall quality ofthe subsequently deposited outermost metal layer, in particular in termsof glance/brightness and surface roughness. This is in particularobserved if the outermost metal layer is a chromium layer.

Since the optical appearance of the outermost metal layer is desired tobe as perfect as possible, a suitable method for metallizing starts witha well-balanced etching step.

Objective of the Present Invention

It is therefore the objective of the present invention to overcome theabove mentioned shortcomings of the prior art.

It is in particular an objective of the present invention to provide amethod for metallizing a non-metallic substrate, wherein the obtainedmetallized substrate (in particular with a chromium layer) provides aneven further improved quality. It is in particular demanded to obtain ametal layer (in particular a chromium layer), which is very smooth andhas an improved metallic glance/brightness, but still being sufficientlyadhered to the non-metallic substrate.

It is furthermore an objective of the present invention to provide amethod including a single pre-treatment step, in particular withoutchemical reducing steps.

It is another objective to provide a method that is less dependent onsubstrates with high manufacturing quality but rather also allows ahomogeneous pre-treatment and metallization, respectively, of substratesof lower manufacturing quality, in particular substrates comprisingpolybutadiene.

SUMMARY OF THE INVENTION

Above mentioned objectives are solved by a method for metallizing anon-metallic substrate, the method comprising the steps

-   -   (A) contacting the non-metallic substrate with a pre-treatment        composition such that a pre-treated substrate is obtained,        -   wherein the pre-treatment composition comprises        -   (A-a) individual manganese (II), (III), and (IV) species,    -   (B) contacting the pre-treated substrate with an activation        composition such that an activated substrate is obtained, and    -   (C) contacting the activated substrate with one or more than one        metalizing composition such that a metalized substrate is        obtained,    -   with the proviso that        -   in the pre-treatment composition, the total concentration of            manganese (IV) species is higher than the combined            concentration of manganese (II) and (III) species,        -   an electrical current is applied to the pre-treatment            composition such that manganese (II) species are oxidized to            manganese (III) species, and        -   in step (A) contacting said substrate with manganese species            is carried out in a single step.

The present invention is primarily based on a specifically designedpre-treatment composition utilized in step (A); most preferably incombination with a metalizing composition comprising nickel for nickelplating in step (C). Said specifically designed pre-treatmentcomposition comprises individual manganese (II), (III), and (IV)species. This means that throughout the method, the pre-treatmentcomposition comprises at least three distinct manganese species, whichare different from each other. All three species are simultaneouslypresent. In the context of the present invention, the term “manganese(II), (III), and (IV)” denotes the element manganese with the oxidationnumbers +2, +3, and +4, respectively, in respective compounds and/orions.

Preferred is a method of the present invention, wherein the individualmanganese (II), (III), and (IV) species are present in a steady state inthe pre-treatment composition during step (A).

The method of the present invention results in a unique, finesponge-like etch pattern/structure leading to a sufficient roughening ofthe substrate without causing too deep or large cavities (i.e. softetching). Although deep and/or large cavities are typically desired inorder to obtain a strong adhesion to a metal layer, our owninvestigations show that such deep/strong cavities often negativelyaffect the optical appearance of the final decorative layer (e.g. achromium layer), in particular in terms of brightness and uniformity.Such deep/strong cavities (which are undesired in the context of thepresent invention) are typically obtained if the substrate is contactedwith a composition comprising suitable amounts of manganese (VII)species, in particular permanganate ions. In contrast, said finesponge-like etch pattern/structure, which is seemingly a disadvantage,is in fact a great advantage of the present invention. This is inparticular the case if the substrates are of varying manufacturingquality; a problem sometimes observed for substrates comprisingbutadiene moieties, preferably polybutadiene. Often such defects are aresult of varying manufacturing parameters during a casting process,typically leading to an inhomogeneous material distribution or othermanufacturing defects. Such defects are not necessarily outwardly seenright from the beginning but often become obvious or at least pronouncedduring the pre-treatment step. However, if the pre-treatment steppronounces such defects, the optical quality of a respective metallizedsubstrate is in many cases deteriorated particularly at such areas ofthe substrate.

It was surprising that the method of the present invention did not onlyproduced fine results with high quality substrates but still veryacceptable results for substrates with manufacturing defects, i.e. lowermanufacturing quality. In most cases a still very homogeneous opticalappearance of the metallized substrate was obtained due to the lesspronounced manufacturing defects. As a result, the method of the presentinvention allows a metallization of substrates that otherwise would bediscarded.

In the method of the present invention an electrical current is appliedto the pretreatment composition such that manganese (II) species areoxidized to manganese (III) species, preferably continually. By that,further procedural advantages are obtained.

First, in the method of the present invention, no strongly adheringparticulate manganese dioxide is formed during step (A) which otherwisemust be chemically reduced by contacting the substrate with acomposition comprising a reducing agent. Instead, it is easily removedby a simple rinsing, which is typically anyways applied (preferably withwater). Since it does not strongly adhere to the substrate (i.e. theyare not incorporated onto the substrate), removal is quickly and easilyaccomplished.

Second, the electrical current allows to keep the individual manganese(II), (III), and (IV) species in individual and comparatively constantconcentration ranges, which would be not achievable without anelectrical current. Furthermore, some manganese species, in particularthe manganese (III) species, would not be present without the appliedelectrical current. As a result, without wishing to be bound to anytheory, the presence of the individual manganese (II), (III), and (IV)species in the pre-treatment composition, caused by the electricalcurrent, are essential to achieve the advantages mentioned above. Themanganese species primarily needed for the excellent pre-treating resultis believed to be the manganese (IV) species.

In addition, the electrical current preferably decomposes water thattypically accumulates in the pre-treatment composition, e.g. due tohygroscopic effects. Thus, the quality of the pre-treatment compositionmaintains stable (e.g. in terms of density).

DETAILED DESCRIPTION OF THE INVENTION

The method of the present invention primarily includes a contacting witha specific pre-treatment composition in order to obtain a particularlypre-treated substrate.

Preferred is a method of the present invention, wherein in step (A) thepre-treatment composition is an etching-composition for etching thenon-metallic substrate, preferably a non-metallic substrate as definedas being preferred throughout the present text.

Step (A):

The Non-Metallic Substrate:

Preferred is a method of the present invention, wherein the non-metallicsubstrate comprises, preferably is, a non-conductive substrate.

Preferred is a method of the present invention, wherein the non-metallicsubstrate comprises, preferably is, a plastic substrate.

More preferred is a method of the present invention, wherein thenon-metallic substrate (and the non-conductive substrate, respectively)comprises butadiene moieties, preferably polybutadiene.

Also preferred is a method of the present invention, wherein thenon-metallic substrate (and the non-conductive substrate, respectively)comprises nitrile moieties.

Also preferred is a method of the present invention, wherein thenon-metallic substrate (and the non-conductive substrate, respectively)comprises acryl moieties.

Also preferred is a method of the present invention, wherein thenon-metallic substrate (and the non-conductive substrate, respectively)comprises styrene moieties.

Most preferred is a method of the present invention, wherein thenon-metallic substrate comprises, preferably is,acrylonitrile-butadiene-styrene (ABS) and/oracrylonitrile-butadiene-styrene-polycarbonate (ABS-PC).

The Pre-Treatment Composition:

The pre-treatment composition utilized in the method of the presentinvention comprises water. Preferably, the pre-treatment compositioncomprises less than 50 wt. % water, based on the total weight of thepre-treatment composition, preferably 45 wt.-% or less, more preferably40 wt.-% or less, even more preferably 35 wt.-% or less, yet even morepreferably 30 wt.-% or less, most preferably 25 wt.-% or less.

Preferred is a method of the present invention, wherein thepre-treatment composition comprises water ranging from 0 wt.-% to 25wt.-%, based on the total weight of the pre-treatment composition,preferably from 0.1 wt.-% to 21 wt.-%, more preferably from 1 wt.-% to18 wt.-%, even more preferably from 2 wt.-% to 16 wt.-%, yet even morepreferably from 5 wt.-% to 14 wt.-%, most preferably from 8 wt.-% to 12wt.-%. Most preferably, water is the only solvent in the pre-treatmentcomposition.

In the method of the present invention the pre-treatment compositioncomprise specific manganese species. Other manganese species are lesspreferred or are most preferably to be avoided entirely.

Preferred is a method of the present invention, wherein in step (A) thepre-treatment composition is substantially free of, preferably does notcomprise, manganese (VII) species, or only up to a total concentrationof 100 mg/L, based on the total volume of the pre-treatment compositionand on the element manganese, preferably only up to a totalconcentration of 75 mg/L, more preferably only up to a totalconcentration of 50 mg/L, even more preferably only up to a totalconcentration of 35 mg/L, most preferably only up to a totalconcentration of 20 mg/L, even most preferably only up to a totalconcentration of 10 mg/L. Own experiments indicate that an insignificantlow amount (e.g. as an impurity or unavoidable side reaction) of suchmanganese species is tolerable. However, preferred is a method of thepresent invention, wherein the pre-treatment composition comprisesmanganese (VII) species in a concentration from 0 mg/L to 10 mg/L, basedon the total volume of the pre-treatment composition.

If present, manganese (VII) species are preferably formed (preferablyonly) in situ, most preferably up to a concentration range as definedabove. This means that manganese (VII) species, are preferably notintentionally/purposely added to the pre-treatment composition.

Preferred is a method of the present invention, wherein in step (A) thepre-treatment composition is substantially free of, preferably does notcomprise, permanganate ions, or only up to a total concentration of 100mg/L, based on the total volume of the pre-treatment composition and theelement manganese, preferably only up to a total concentration of 75mg/L, more preferably only up to a total concentration of 50 mg/L, evenmore preferably only up to a total concentration of 35 mg/L, mostpreferably only up to a total concentration of 20 mg/L, even mostpreferably only up to a total concentration of 10 mg/L. Theaforementioned regarding manganese (VII) species preferably applieslikewise.

If present at all, permanganate ions are preferably formed (preferablyonly) in situ, most preferably up to a concentration range as definedabove. This means, that permanganate ions are preferably notintentionally/purposely added to the pre-treatment composition.

Preferred is a method of the present invention, wherein thepre-treatment composition is substantially free of, preferably does notcomprise, a methane sulfonic acid and salts thereof, preferably issubstantially free of, preferably does not comprise, a C1 to C4 alkylsulfonic acid and salts thereof, most preferably is substantially freeof, preferably does not comprise, a C1 to C4 sulfonic acid and saltsthereof. It appears that such compounds negatively affect the waterbalance in a respective pretreatment composition.

Preferred is a method of the present invention, wherein thepre-treatment composition is substantially free of, preferably does notcomprise, bromide and iodide anions, preferably is substantially freeof, preferably does not comprise, chloride, bromide, and iodide anions,most preferably is substantially free of, preferably does not comprise,halide anions.

Preferred is a method of the present invention, wherein thepre-treatment composition is substantially free of, preferably does notcomprise, trivalent chromium ions and hexavalent chromium compounds,preferably is substantially free of, preferably does not comprise, anycompounds and ions comprising chromium.

Preferred is a method of the present invention, wherein thepre-treatment composition is substantially free of, preferably does notcomprise, manganese (V) species, or only up to a total concentration of100 mg/L, based on the total volume of the pretreatment composition andthe element manganese, preferably only up to a total concentration of 75mg/L, more preferably only up to a total concentration of 50 mg/L, evenmore preferably only up to a total concentration of 35 mg/L, mostpreferably only up to a total concentration of 20 mg/L, even mostpreferably only up to a total concentration of 10 mg/L. Most preferably,manganese (V) species are not detectable, preferably via UV/VISspectroscopy. Preferably they are not intentionally/purposely added tothe pre-treatment composition.

Preferred is a method of the present invention, wherein thepre-treatment composition is substantially free of, preferably does notcomprise, manganese (VI) species, or only up to a total concentration of100 mg/L, based on the total volume of the pretreatment composition andthe element manganese, preferably only up to a total concentration of 75mg/L, more preferably only up to a total concentration of 50 mg/L, evenmore preferably only up to a total concentration of 35 mg/L, mostpreferably only up to a total concentration of 20 mg/L, even mostpreferably only up to a total concentration of 10 mg/L. Most preferably,manganese (VI) species are not detectable, preferably via UV/VISspectroscopy. Preferably they are not intentionally/purposely added tothe pre-treatment composition.

As mentioned, the pre-treatment composition comprises individualmanganese (II), (III), and (IV) species. Preferred is a method of thepresent invention, wherein during step (A) in the pre-treatmentcomposition the total amount of all manganese species is more than 5.0g/L, based on the total volume of the pre-treatment composition and theelement manganese, preferably is 5.4 g/L or more, even more preferablyis 5.8 g/L or more, most preferably is 6.0 g/L or more. A preferredmaximum concentration is up to 7.5 g/L, based on the total volume of thepre-treatment composition and the element manganese, preferably up to7.2 g/L, more preferably up to 7.0 g/L, even more preferably up to 6.8g/L, yet even more preferably up to 6.6 g/L, most preferably up to 6.3g/L.

Preferred is a method of the present invention, wherein in thepre-treatment composition manganese (III) species disproportionate tomanganese species comprising manganese (IV) species.

Preferred is a method of the present invention, wherein the manganese(II) species comprise, preferably are, Mn(II) ions.

Preferred is a method of the present invention, wherein during step (A)in the pretreatment composition the manganese (II) species have a totalconcentration in a range from 0.1 g/L to 0.8 g/L, based on the totalvolume of the pre-treatment composition and the element manganese,preferably from 0.15 g/L to 0.7 g/L, more preferably from 0.2 g/L to 0.6g/L, most preferably from 0.25 g/L to 0.5 g/L. This preferably includesall manganese species as long as the element manganese has the oxidationnumber +2.

A preferred source of manganese (II) species is manganese (II) sulfate.

Preferred is a method of the present invention, wherein the manganese(III) species comprise, preferably are, Mn(III) ions.

Preferred is a method of the present invention, wherein during step (A)in the pretreatment composition the manganese (III) species have a totalconcentration in a range from 0.2 g/L to 1.9 g/L, based on the totalvolume of the pre-treatment composition and the element manganese,preferably from 0.3 g/L to 1.5 g/L, more preferably from 0.4 g/L to 1.2g/L, even more preferably from 0.5 g/L to 1.0 g/L, most preferably from0.6 g/L to 0.8 g/L.

Preferred is a method of the present invention, wherein in thepre-treatment composition during step (A) the manganese (III) specieshave a higher total concentration than the manganese (II) species.Preferably, based on the element manganese, more preferably this appliesto concentrations in g/L, based on the total volume of the pre-treatmentcomposition and the element manganese in these manganese species.

Preferred is a method of the present invention, wherein the manganese(IV) species comprise colloidal manganese (IV) species, preferablycomprise a mixture of colloidal manganese (IV) species and manganese(IV) ions.

Preferred is a method of the present invention, wherein during step (A)in the pretreatment composition the manganese (IV) species have a totalconcentration in a range from 1.5 g/L to 5.0 g/L, based on the totalvolume of the pre-treatment composition and the element manganese,preferably from 1.8 g/L to 4.5 g/L, more preferably from 2.0 g/L to 4.0g/L, even more preferably from 2.2 g/L to 3.5 g/L, most preferably from2.4 g/L to 3.0 g/L.

Preferred is a method of the present invention, wherein in thepre-treatment composition more than 50 wt.-% of the manganese (IV)species, based on the total weight of all manganese (IV) species andbased on the element manganese, comprise colloidal manganese (IV)species, preferably 60 wt.-% or more, more preferably 65 wt.-% or more,most preferably 70 wt.-% or more. Preferably, the colloidal manganese(IV) species comprises manganese dioxide.

In the pre-treatment composition utilized in the method of the presentinvention, the total concentration of manganese (IV) species is higherthan the combined concentration of manganese (II) and (III) species.Preferably, based on the element manganese, this applies toconcentrations in g/L, based on the total volume of the pretreatmentcomposition and the element manganese in each individual manganesespecies.

Preferred is a method of the present invention, wherein during step (A)in the pretreatment composition 55 wt.-% or more are manganese (IV)species, based on the total weight of all manganese species and theelement manganese, preferably 59 wt.-% or more, more preferably 63 wt.-%or more, even more preferably 67 wt.-% or more, most preferably 70 wt.-%or more.

Preferred is a method of the present invention, wherein thepre-treatment composition is acidic, preferably has a pH of 3.0 orbelow, more preferably of 2.1 or below, even more preferably of 1.5 orbelow, most preferably of 1.0 or below, even most preferably of 0.7 orbelow. Preferably, the strong acidic condition is a result of acidsbeing present in the pre-treatment composition.

Preferred is a method of the present invention, wherein thepre-treatment composition additionally comprises

-   -   (A-b) one, two or more than two (preferably two) acids,        preferably inorganic acids, most preferably at least a        combination of sulfuric acid and phosphoric acid.

Preferred is a method of the present invention, wherein thepre-treatment composition comprises sulfuric acid in a totalconcentration of 10 mol/L or less, based on the total volume of thepre-treatment composition, preferably of 9.6 mol/L or less, morepreferably of 9.1 mol/L or less, most preferably of 8.6 mol/L or less.

Preferred is a method of the present invention, wherein thepre-treatment composition comprises sulfuric acid in a totalconcentration of at least 3.0 mol/L, based on the total volume of thepre-treatment composition, preferably of at last 3.5 mol/L, morepreferably of at least 4.0 mol/L, most preferably of at least 4.5 mol/L.

Preferred is a method of the present invention, wherein in thepre-treatment composition the sulfuric acid has a concentration in arange from 3 mol/L to below 10 mol/L, based on the total volume of thepre-treatment composition, preferably from 3.5 mol/L to 8 mol/L, morepreferably from 4 mol/L to 6 mol/L, most preferably from 4.5 mol/L to5.5 mol/L.

Preferred is a method of the present invention, wherein thepre-treatment composition comprises at least a combination of sulfuricacid and phosphoric acid, wherein the phosphoric acid has a higherconcentration than the sulfuric acid, preferably the molar ratio ofphosphoric acid to sulfuric acid is in a range from 1.1:1 to 3:1, morepreferably is in a range from 1.3:1 to 2.6:1, even more preferably is ina range from 1.4:1 to 2.4:1, yet even more preferably is in a range from1.5:1 to 2.1:1, most preferably is in a range from 1.6:1 to 2.0:1.

In the context of the present invention it is most preferable that thephosphoric acid has a higher concentration than sulfuric acid.Typically, sulfuric acid incorporates a comparatively high amount ofwater due to hygroscopic effects. This leads to an undesired dilution ofthe pre-treatment composition. If the concentration of sulfuric acid isminimized to the best extent possible, such a dilution is minimized too.Own experiments have shown that the concentrations and molar ratios asdefined above for sulfuric acid result in an excellent balance betweenwater accumulation on the one hand and water decomposition by means ofthe electrical current on the other hand. This allows to keep thepre-treatment composition under stable condition (stable water-balance).

Preferred is a method of the present invention, wherein thepre-treatment composition has an absorbance of more than 1.0, referencedto a wavelength of 400 nm and preferably a path length of 1 cm,preferably in a range from 1.1 to 2.1, more preferably from 1.2 to 2.0,most preferably from 1.3 to 1.7. If the absorbance is significantlybelow 1.0, typically an undesired low adhesion between the non-metallicsubstrate and the metal layers applied in step (C) is often observed(e.g. <0.5 N/cm). In contrast, if the absorbance is above 1.0, moreparticularly in the preferred ranges as mentioned above, typically agood adhesion (e.g. >1.0 N/cm) is even observed. This parameter is apreferred quality parameter to evaluate whether the three manganesespecies are properly present in the pre-treatment composition.

Preferably, the absorbance (also named extinction) is determined viaUV/VIS spectroscopy with a path length of 1 cm at 400 nm (Beer-Lambertlaw).

Preferred is a method of the present invention, wherein thepre-treatment composition additionally comprises

-   -   (A-c) one or more than one species of additional transition        metal ions different from manganese.

Preferred is a method of the present invention, wherein in thepre-treatment composition the one or more than one species of additionaltransition metal ions different from manganese has a total concentrationin a range from 1 mmol/L to 50 mmol/L, based on the total volume of thepre-treatment composition, preferably from 2 mmol/L to 40 mmol/L, morepreferably from 3 mmol/L to 30 mmol/L, even more preferably from 4mmol/L to 20 mmol/L, most preferably from 5 mmol/L to 15 mmol/L.

Preferred is a method of the present invention, wherein in thepre-treatment composition the one or more than one species of additionaltransition metal ions different from manganese comprise silver ions,said silver ions preferably having a total concentration in a range from4 mmol/L to 25 mmol/L, based on the total volume of the pre-treatmentcomposition, preferably from 6 mmol/L to 20 mmol/L, more preferably from8 mmol/L to 17 mmol/L, most preferably from 10 mmol/L to 14 mmol/L. Verypreferably, said silver ions are the only additional transition metalions. In the context of the present invention, the aforementioned totalconcentration of silver ions includes silver ions with any oxidationnumber. Since silver ions are preferably present, halide ions, inparticular chloride ions, are to be avoided to prevent precipitation.

Preferred is a method of the present invention, wherein the silver ionshave an oxidation number of +1, most preferably the silver ions added tothe pre-treatment composition.

Preferred is a method of the present invention, wherein thepre-treatment composition additionally comprises

-   -   (A-d) one or more than one wetting agent, preferably a        fluorinated wetting agent.

Preferred is a method of the present invention, wherein the one or morethan one wetting agent (preferably the fluorinated wetting agent) ispresent in the pre-treatment composition in a total concentration in arange from 0.001 g/L to 1.0 g/L, based on the total volume of thepre-treatment composition, preferably in a range from 0.005 g/L to 0.7g/L, more preferably in a range from 0.01 g/L to 0.5 g/L, even morepreferably in a range from 0.02 g/L to 0.3 g/L, most preferably in arange from 0.03 g/L to 0.15 g/L. Preferably, the fluorinated wettingagent is partly or fully fluorinated or a mixture thereof (if e.g. morethan one wetting agent is present).

Preferred is a method of the present invention, wherein thepre-treatment composition additionally comprises

-   -   (A-e) peroxomonosulfate anions and/or peroxodisulfate anions,        preferably in a total concentration in a range from 0.01 g/L to        10.0 g/L, based on the total volume of the pre-treatment        composition, preferably from 0.05 g/L to 7.0 g/L, more        preferably from 0.1 g/L to 4.0 g/L, even more preferably from        0.2 g/L to 2.0 g/L, most preferably from 0.1 g/L to 0.5 g/L.

In some rare cases, preferred is a method of the present invention,wherein the pretreatment composition additionally comprises

-   -   (A-f) peroxomonophosphate anions and/or peroxodiphospate anions,        preferably in a total concentration in a range from 0.01 g/L to        10.0 g/L, based on the total volume of the pre-treatment        composition, preferably from 0.05 g/L to 9.0 g/L, more        preferably from 0.07 g/L to 8.0 g/L, even more preferably from        0.09 g/L to 7.0 g/L, most preferably from 0.1 g/L to 5.0 g/L.

Preferred is a method of the present invention, wherein thepre-treatment composition additionally comprises

-   -   (A-g) nitrate anions, preferably in a total concentration in a        range from 0.01 g/L to 20.0 g/L, based on the total volume of        the pre-treatment composition, preferably from 0.05 g/L to 17.0        g/L, more preferably from 0.1 g/L to 13.0 g/L, even more        preferably from 0.25 g/L to 9.0 g/L, most preferably from 0.5        g/L to 5.0 g/L.

Preferably, the source of nitrate anions is silver nitrate. Mostpreferably, the total concentration of nitrate anions corresponds to thetotal concentration of silver ions. Most preferably, the only source ofsilver ions and nitrate anions is silver nitrate.

Preferably, aforementioned components (A-c), (A-e), (A-f), and (A-g)support the electrochemical reactions in the pre-treatment composition.

Preferred is a method of the present invention, wherein thepre-treatment composition has a density in a range from 1.50 g/cm³ to1.90 g/cm³, referenced to a temperature of 25° C., preferably from 1.55g/cm³ to 1.80 g/cm³, more preferably from 1.60 g/cm³ to 1.70 g/cm³, mostpreferably from 1.61 g/cm³ to 1.68 g/cm³. Such a density range indicatesthat a suitable water-balance is provided.

The Contacting:

Preferred is a method of the present invention, wherein in step (A)primarily polybutadiene is pre-treated, preferably etched, if thesubstrate comprises, preferably is, acrylonitrile-butadiene-styrene(ABS) and/or acrylonitrile-butadiene-styrene-polycarbonate (ABS-PC),most preferably polybutadiene is more pre-treated, preferably etched,than the acrylonitrile styrene.

Preferred is a method of the present invention, wherein the substrateand pretreated substrate, respectively, is additionally not contactedwith a composition comprising permanganate ions, preferably isadditionally not contacted with a composition comprising manganese (VII)species.

More preferred is a method of the present invention, wherein thesubstrate and pretreated substrate, respectively, is not contacted withany composition comprising permanganate ions in a total concentration of2 g/L or more, based on the total volume of said composition, preferablyof 1 g/L or more, even more preferably of 500 mg/L or more, yet evenmore preferably of 250 mg/L or more, most preferably of 150 mg/L ormore.

Even more preferred is a method of the present invention, wherein thesubstrate and pre-treated substrate, respectively, is not contacted withany composition comprising manganese (VII) species. This most preferablyapplies if the pre-treatment composition utilized in the method of thepresent invention is substantially free of, preferably does notcomprise, manganese (VII) species.

Preferred is a method of the present invention, wherein during step (A)substantially no, preferably no, manganese dioxide (MnO₂) isincorporated onto the pre-treated substrate. Thus, in the method of thepresent invention, no step is needed (and therefore not applied) inorder to reduce manganese dioxide on the pre-treated substrate; i.e. inorder to dissolve MnO₂ by chemical reduction through a reducing agent.Thus, preferably, the pre-treated substrate obtained after step (A) isnot contacted with a respective composition comprising a reducing agent.

Instead, preferred is a method of the present invention, wherein afterstep (A) or prior to step (B) manganese dioxide adsorbed on thepre-treated substrate (preferably if present) is removed by rinsing,preferably by rinsing with water, more preferably by rinsing with waterfree of a reducing agent capable to chemically reduce manganese dioxide.

Preferred is a method of the present invention, wherein during step (A)or prior to step (B) the pre-treated substrate is not contacted with acomposition comprising a reducing agent capable to chemically reducemanganese dioxide, preferably is not contacted with a compositioncomprising any reducing agent.

Due to the specific composition of the pre-treatment composition and howit is utilized in the method of the present invention, such a step isnot required.

Preferred is a method of the present invention, wherein in step (A) thepre-treatment composition has a temperature in a range from 15° C. to60° C., preferably from 20° C. to 55° C., more preferably from 27° C. to50° C., even more preferably from 34° C. to 46° C., most preferably from38° C. to 43° C.

Preferred is a method of the present invention, wherein step (A) iscarried out for a time ranging from 1 minute to 25 minutes, preferablyfrom 5 minutes to 20 minutes, most preferably from 10 minutes to 18minutes.

The Electrical Current:

Preferred is a method of the present invention, wherein during step (A)the electrical current is continuously applied.

Preferred is a method of the present invention, wherein during step (A)the manganese (III) species is continuously formed through theelectrical current.

Preferred is a method of the present invention, wherein the electricalcurrent has an anodic current density in a range from 0.1 A/dm² to 20A/dm², preferably from 0.8 A/dm² to 15 A/dm², more preferably from 1.5A/dm² to 10 A/dm², most preferably from 2.1 A/dm² to 5.0 A/dm².

Preferred is a method of the present invention, wherein during step (A)the pretreatment composition is exposed to a current load by theelectrical current ranging from 0.5 Ah/L to 100 Ah/L, based on the totalvolume of the pre-treatment composition, preferably ranging from 1.0Ah/L to 70 Ah/L, more preferably ranging from 2.0 Ah/L to 50 Ah/L, mostpreferably ranging from 4.0 Ah/L to 30 Ah/L.

Pre-Treatment Compartment:

Preferred is a method of the present invention, wherein step (A) iscarried out in a pre-treatment compartment comprising at least onecathode and at least one anode, preferably comprising at least onecathode, at least one anode, and at least one membrane, such that saidmanganese (II) species are oxidized to said manganese (III) species inthe pre-treatment compartment.

Alternatively but more preferred is a method of the present invention,wherein step (A) is carried out in a pre-treatment compartmentfluidically connected with an oxidizing compartment, the oxidizingcompartment comprising at least one cathode and at least one anode,preferably comprising at least one cathode, at least one anode, and atleast one membrane, such that said manganese (II) species are oxidizedto said manganese (III) species in the oxidizing compartment. In such apreferred method of the present invention, the pre-treatment compartmentpreferably does not comprise a cathode and an anode. In such a case, thepre-treatment composition preferably circulates continually orsemi-continually between the pre-treatment compartment and the oxidizingcompartment.

Preferred is a method of the present invention, wherein said individualmanganese (II), (III), and (IV) species are migrating (preferablycirculating) between the pretreatment compartment and the oxidizingcompartment.

Preferred is a method of the present invention, wherein the electricalcurrent is applied in the oxidizing compartment.

Preferred is a method of the present invention, wherein the at least oneanode comprises a mixed metal anode or a graphite anode.

A preferred mixed metal anode comprises at least two of lead, tin,silver, titanium, and platinum.

A more preferred mixed metal anode comprises at least lead and tin, evenmore preferably at least lead, tin, and silver. Our own experiments haveshown that the preparation of a respective pre-treatment compositionwhile using anodes comprising lead, tin, and silver, is significantlyshorter than using anodes comprising lead and tin but without silver.

Most preferred is a mixed metal anode comprising lead, 0.1 wt.-% to 3.0wt.-% silver, and 1.0 wt.-% to 10.0 wt.-% tin, based on the total weightof the mixed metal anode. Preferably, the balance to 100 wt.-% is lead.

Preferred is a method of the present invention, wherein the mixed metalanode comprises 0.2 wt.-% to 2.0 wt.-% silver, based on the total weightof the mixed metal anode.

Preferred is a method of the present invention, wherein the at least onecathode is a mixed metal cathode or a graphite cathode, preferably is amixed metal cathode, even more preferably comprising at least lead andtin, most preferably is a mixed metal cathode comprising at least leadand 1.0 wt.-% to 10.0 wt.-% tin, based on the total weight of the atleast one cathode.

Preferred is a method of the present invention, wherein the at least oneanode has a total anode surface and the at least one cathode has a totalcathode surface, wherein the total anode surface to the total cathodesurface has a ratio of 2:1 or more, preferably of 3:1 or more, morepreferably of 4:1 or more, most preferably of 5:1 or more.

Step (B):

In step (B) of the method of the present invention, the pre-treatedsubstrate is contacted with an activation composition. Step (A) includesall steps carried out prior to step (B), preferably including a rinsingand further optional steps carried out prior to and/or after step (A),e.g. a swelling and/or a conditioning step.

Particularly preferred in some cases is a method of the presentinvention comprising prior to step (B) but after the contacting with thepre-treatment composition a conditioning step with a conditioningcomposition, i.e. a contacting with a conditioning composition. Ownexperiments have shown that such a conditioning step significantlyincreases (and thereby improves) the adsorption of palladium in step(B). In other words, the total amount of palladium adsorbed andattached, respectively, on the non-metallic substrate after step (B) isfinished, is significantly increased compared to a method of the presentinvention without such a conditioning step. In some cases, the adsorbed,respectively attached, total amount is sufficient for a subsequentso-called direct metallization. Generally, such a conditioning stepreduces the amount of wasted palladium due to the increased adsorption(and therefore increased efficiency) in step (B).

Preferably, after the contacting with the conditioning composition, thenon-metallic substrate is rinsed in a rinse step, preferably is at leastonce rinsed with water.

Preferred is a method of the present invention, wherein the conditioningcomposition is alkaline, preferably has a pH ranging from 9 to 14, morepreferably from 10 to 13.5, even more preferably from 11 to 13, mostpreferably from 11.5 to 12.5.

Preferred is a method of the present invention, wherein the conditioningcomposition comprises an amine-compound, preferably a diamine-compound.

More preferred is a method of the present invention, wherein theconditioning composition comprises at least two amine-compounds,preferably at least two diamine-compounds.

A preferred amine-compound and diamine-compound, respectively, comprisesan alkyl moiety, preferably an alkyl moiety having 2 to 12 carbon atoms,preferably 2 to carbon atoms, more preferably 2 to 8 carbon atoms, mostpreferably 2 to 6 carbon atoms. Most preferably this denotes analkylene, i.e. a divalent, moiety if it relates to a diamine.

A very preferred diamine-compound comprises hexane diamine, i.e.hexamethylene diamine (most preferably hexane-1,6-diamine) and/or ethanediamine, i.e. ethylene diamine (most preferably ethane-1,2-diamine).

Preferred is a method of the present invention, wherein the conditioningstep is carried out for 0.1 minutes to 15 minutes, preferably for 0.2minutes to 11 minutes, more preferably for 0.3 minutes to 8 minutes,even more preferably for 0.4 minutes to 5 minutes, most preferably for0.5 minutes to 2.5 minutes.

Preferred is a method of the present invention, wherein in theconditioning step the conditioning composition has a temperature rangingfrom 25° C. to 50° C., preferably from 28° C. to 46° C., more preferablyfrom 30° C. to 42° C., even more preferably from 32° C. to 39° C., mostpreferably from 34° C. to 37° C.

In the method of the present invention, preferably step (B) is a stepseparated and independently from step (A). In other words, thepre-treatment composition utilized in step (A) is not the activationcomposition utilized in step (B).

Preferred is a method of the present invention, wherein in step (B) theactivation composition comprises palladium, preferably dissolvedpalladium ions or colloidal palladium, most preferably colloidalpalladium. Preferably, the colloidal palladium comprises tin.

Preferred is a method of the present invention, wherein in step (B) theactivation composition comprises palladium in a total concentrationranging from 20 mg/L to 200 mg/L, based on the total volume of theactivation composition, preferably ranging from 40 mg/L to 150 mg/L,even more preferably from 50 mg/L to 110 mg/L, most preferably from 55mg/L to 80 mg/L. Preferably, this total concentration includes bothdissolved palladium ions and colloidal palladium. Above concentrationsare based on the element palladium.

Preferred is a method of the present invention, wherein in step (B) theactivation composition has a temperature ranging from 25° C. to 70° C.,preferably from 30° C. to 60° C., even more preferably from 36° C. to50° C., most preferably from 39° C. to 46° C.

Preferred is a method of the present invention, wherein in step (B) thecontacting is carried out for a time ranging from 1 minute to 15minutes, preferably from 2 minutes to 12 minutes, even more preferablyfrom 3 minutes to 9 minutes, most preferably from 4 minutes to 7minutes.

Preferred is a method of the present invention, wherein step (B)comprises step

-   -   (B-1) contacting the activated substrate with an accelerator        composition to modify the activated substrate, the accelerator        composition comprising        -   no reducing agent but at least one complexing agent for tin            ions, if in step (B) the activation composition comprises            colloidal palladium, or        -   a reducing agent for reducing palladium ions to metallic            palladium, if in step (B) the activation composition            comprises palladium ions but no colloidal palladium.

Preferred is a method of the present invention, wherein in step (B-1)the accelerator composition comprises no reducing agent but at least onecomplexing agent for tin ions and is acidic, preferably comprising inaddition sulfuric acid.

In the context of the present invention, step (B-1) as defined above iscarried out after contacting the pre-treated substrate with anactivation composition such that an activated substrate is obtained.

Step (C):

In step (C) of the method of the present invention, the activatedsubstrate is metallized. Preferred is a method of the present invention,wherein step (C) comprises a contacting with at least one metalizingcomposition comprising nickel ions, preferably comprises a contactingwith at least two distinct metalizing compositions each comprisingnickel ions, most preferably prior to a contacting with a metalizingcomposition comprising copper ions. Most preferably the at least one,preferably the at least two, metalizing compositions are for depositinga nickel and/or a nickel alloy metal layer, respectively.

In agreement with this, preferred is a method of the present invention,wherein step (C) comprises step

-   -   (C-1) contacting the activated substrate with a first metalizing        composition for electroless plating to obtain a metalized        substrate having a first nickel/nickel alloy metal layer,        wherein the first metalizing composition comprises nickel ions        and a reducing agent for nickel ions.

Preferred is a method of the present invention, wherein in step (C-1)the first metalizing composition is alkaline, preferably has a pHranging from 8.0 to 11.0, preferably from 8.2 to 10.2, more preferablyfrom 8.4 to 9.3, most preferably from 8.6 to 9.0.

Preferred is a method of the present invention, wherein in step (C-1)the first metalizing composition has a temperature ranging from 18° C.to 60° C., preferably from 20° C. to 55° C., even more preferably from23° C. to 50° C., most preferably from 26° C. to 45° C.

Preferred is a method of the present invention, wherein step (C)comprises after step (C-1) step

-   -   (C-2) contacting the metalized substrate having the first        nickel/nickel alloy metal layer with a second metalizing        composition for electrolytic plating to obtain a metalized        substrate with a second nickel/nickel alloy metal layer, wherein        the second metalizing composition comprises nickel ions and is        preferably substantially free of, preferably does not comprise,        a reducing agent for nickel ions.

Preferred is a method of the present invention, wherein in step (C-2)the second metalizing composition is acidic, preferably has a pH rangingfrom 1.0 to 5.0, preferably from 2.0 to 4.5, more preferably from 2.8 to4.0, most preferably from 3.3 to 3.7.

Preferred is a method of the present invention, wherein in step (C-2)the second metalizing composition has a temperature ranging from 25° C.to 70° C., preferably from 35° C. to 65° C., even more preferably from45° C. to 61° C., most preferably from 52° C. to 58° C.

Preferred is a method of the present invention, wherein in step (C-2)the contacting is carried out for a time ranging from 1 minute to 10minutes, preferably from 2 minutes to 8 minutes, most preferably from2.5 minutes to 5.5 minutes.

Preferred is a method of the present invention, wherein in step (C-2) anelectrical current is applied, preferably ranging from 0.3 A/dm² to 10.0A/dm², preferably ranging from 0.5 A/dm² to 8.0 A/dm², more preferablyranging from 0.8 A/dm² to 6.0 A/dm², even more preferably ranging from1.0 A/dm² to 4.0 A/dm², most preferably ranging from 1.3 A/dm² to 2.5A/dm².

Preferred is a method of the present invention, wherein in step (C-2)the second metalizing composition comprises chloride ions and/or(preferably and) boric acid.

Preferred is a method of the present invention, wherein in step (C-2)the second metalizing composition is a Watts Nickel composition. Thus,preferred is a method of the present invention, wherein in step (C-2)the second metalizing composition comprises chloride ions, sulfate ions,and boric acid.

Although significantly less preferred, preferred is an alternativemethod of the present invention, wherein step (C) comprises after step(C-1) step

-   -   (C-2) contacting the metalized substrate having the first        nickel/nickel alloy metal layer with a second metalizing        composition to obtain a metalized substrate with a copper/copper        alloy metal layer on the first nickel/nickel alloy metal layer,        wherein the second metalizing composition comprises copper ions        and is preferably an immersion copper metallization composition.

However, as shown below in the examples, in this alternative in somecases an undesired blistering is observed.

Preferred is a method of the present invention, wherein step (C)comprises after step (C-2), most preferably if (C-2) involves nickel,step

-   -   (C-3) contacting the metalized substrate having the second        nickel/nickel alloy metal layer with a third metalizing        composition to obtain a metalized substrate with a copper/copper        alloy metal layer, wherein the third metalizing composition        comprises copper ions.

Preferred is a method of the present invention, wherein in step (C) atleast one metalizing composition of the one or more than one metalizingcomposition comprises trivalent chromium ions such that a chromium orchromium alloy metal layer, respectively, is deposited. Most preferably,the chromium or chromium alloy metal layer, respectively, is theoutermost metallic layer. Thus, most preferably the method of thepresent invention is for metalizing a non-metallic substrate, whereinthe metalizing comprises a chromium deposition, preferably a decorativechromium deposition.

Specifically preferred is a method of the present invention, whereinstep (C) comprises after step (C-3) a further step

-   -   (C-x) contacting the metalized substrate obtained after a step        prior to step (C-x) with a further metalizing composition to        obtain a metalized substrate with a chromium/chromium alloy        metal layer, wherein the further metalizing composition        comprises trivalent chromium ions.

The advantages coming along with the present invention are typicallyobserved and recognized on the chromium/chromium alloy layer.

The present invention furthermore refers to a specific pre-treatmentcomposition comprising

-   -   (A-a) Mn(II) ions, Mn(III) ions, and colloidal manganese (IV)        species,    -   (A-b) one, two or more than two acids,    -   (A-c) silver ions,    -   wherein the pre-treatment composition has        -   a density in a range from 1.50 g/cm³ to 1.90 g/cm³,            referenced to a temperature of 25° C., and        -   an absorbance in a range from 1.1 to 2.1, referenced to a            wavelength of 400 nm and preferably a path length of 1 cm,    -   with the proviso that the pre-treatment composition        -   is substantially free of, preferably does not comprise,            methane sulfonic acid, salts thereof, and chloride ions,        -   is substantially free of, preferably does not comprise,            permanganate ions, or comprises permanganate ions only up to            a total concentration of 100 mg/L, based on the total volume            of the pre-treatment composition and the element manganese,            preferably only up to a total concentration of 75 mg/L, more            preferably only up to a total concentration of 50 mg/L, even            more preferably only up to a total concentration of 35 mg/L,            most preferably only up to a total concentration of 20 mg/L,            even most preferably only up to a total concentration of 10            mg/L.

The aforementioned regarding the method of the present invention and inparticular regarding the pre-treatment composition utilized in themethod of the present invention applies mutatis mutandis to thepre-treatment composition of the present invention (if technicallyapplicable).

EXAMPLES

The invention will now be illustrated by reference to the followingnon-limiting example.

The following method for metallizing a non-metallic substrate wasrepeatedly carried out for at least 3 months with parameters asdescribed below.

A respective pre-treatment composition was prepared as follows in anoxidizing compartment comprising all together 6 tin/lead/silver anodes,12 lead/tin (97 wt.-%/3 wt.-%) anodes, and 9 tin/lead cathodes with atotal cathodic surface to a total anodic surface of approximately 1:2:

First, a mixture of sulfuric and phosphoric acid was added to thecompartment. Manganese (II) sulfate and silver nitrate were added anddissolved in the acid mixture such that the concentration of Mn(II) ions(i.e. the manganese (II) species) is exceeding 5 g/L but below 6 g/L.The silver concentration was about 12 mmol/L.

Second, a current in a range from 1.2 A/dm² to 1.5 A/dm² was applied inorder to oxidize Mn(II) ions to manganese (III) species. After 48 hoursthe pre-treatment composition reached an absorbance at 400 nm of about1.0. The absorbance was measured via UV/VIS spectroscopy with a pathlength of 1 cm.

Third, further amounts of manganese sulfate were added in intervals anddissolved under the effect of the applied current such that finallyafter about 96 hours an absorbance at 400 nm of more than 1.2 wasreached. The density of the pre-treatment composition was finally about1.65 g/L.

The so obtained pre-treatment composition utilized in the method of thepresent invention does not comprise methane sulfonic acid and nointentionally added compounds/ions comprising chromium; in particular nohexavalent chromium compounds. Furthermore, the pre-treatmentcomposition is free of chloride ions and free of intentionally addedpermanganate compounds/ions.

The oxidizing compartment was fluidically connected with a pre-treatmentcompartment (tank volume approximately 5400 liters) such that thepre-treatment composition was allowed to constantly circulate betweenthe pre-treatment compartment and the oxidizing compartment. In thepre-treatment compartment no anodes and no cathodes were installed.

In step (A) of the method of the present invention, a plurality ofnon-metallic plastic substrates (ABS or ABS-PC having surface dimensionsranging from 0.1 dm² to 10 dm² with varying production qualities) wasused. Prior to contacting with the prepared pre-treatment composition inthe pre-treatment compartment, the substrates were cleansed withUniclean 151 (product of Atotech) and afterwards air dried.

Table 1, composition and pre-treatment parameters during step (A)

Pre-treatment composition Mn(II) species [g/L] <0.7 Mn(III) species[g/L] <1.0 Mn(IV) species [g/L] (colloidal) >2.0 Mass portion of Mn(IV)species relative to all >60 detectable manganese species [wt.-%]; basedon element manganese Mn(V) species [g/L] Not detectable* Mn(VI) species[g/L] Not detectable* Mn(VII) species [g/L] Not detectable* Phosphoricacid [mol/L] 9.2 Sulfuric acid [mol/L] 4.3 Silver ions [mmol/L] 12Nitrate anions [g/L] 0.7 Fluorinated wetting agent [g/L] 0.05 Absorbance(1 cm, 400 nm) Approximately 1.2 to 1.3 Density [g/ml] 1.62 to 1.67 pHbelow zero Electrical current in the oxidizing compartment [A/dm²] 1.2to 1.5 Temperature [° C.] 40 Contact time [min] 15 *denotes: determinedby UV/VIS spectroscopy

Concentrations of manganese species are in g/L, based on the totalvolume of the pre-treatment composition and based on the elementmanganese.

During step (A) an electrical current of 1.2-1.5 A/dm² was constantlyapplied to the pre-treatment composition in the oxidizing compartment.

It is noteworthy that during the entire method, all substrates werecontacted with manganese species only in step (A) with the pre-treatmentcomposition as defined in Table 1. No additional contacting was carriedout with a further manganese species-containing composition. Thus, step(A) is a one-step contacting with manganese species and the onlycontacting step with manganese species throughout the entire method.This is a general and important feature of the method of the presentinvention as a whole.

After step (A), pre-treated substrates were obtained with an etchpattern, showing an exceptionally fine sponge-like structure afterremoval of polybutadiene spheres contained in the surface of the ABS andABS-PC, respectively, substrates. Own analysis confirmed that in thesubstrates primarily the polybutadiene frame work was etched wherein theacrylonitrile styrene of the substrates remained primarily intact. As aresult, a very fine-pored surface was obtained after step (A), which wassignificantly less strongly etched compared to substrates contacted withe.g. permanganate ions but still providing sufficient adhesion. It wastherefore an excellent balance obtained between etching and adhesion.

Prior to step (B) a rinsing was carried out with water. If any manganesedioxide particles are present on the substrate, they are simply rinsedaway with water since no strong adherence of manganese dioxide isobserved.

In step (B) the pre-treated substrates were contacted with an activationcomposition comprising colloidal palladium (approximately: 55 mg/L to 80mg/L Pd, temperature 42° C., contact time 5 minutes).

Furthermore, step (B) comprises step (B-1), wherein the pre-treatedsubstrate was contacted with an acidic accelerator composition to modifythe activated substrate, the accelerator composition comprising at leastone complexing agent for tin ions, since in step (B) the activationcomposition comprises colloidal palladium.

Prior to step (C) a rinsing was carried out with water.

In step (C) the activated substrate is contacted with more than onemetalizing composition in order to obtain a metalized substrate.

First, step (C) included step (C-1), wherein the activated substrate wascontacted with an alkaline (pH approximately 8.6 to 9.0) firstmetalizing composition (having a temperature of approximately 26° C. to45° C.; contact time about 10 minutes) for electroless nickel plating.The first metalizing composition comprised approximately 3.5 g/L nickelions and approximately 15 g/L hypophosphite ions as a reducing agent fornickel ions to obtain a metalized substrate having a first nickel alloymetal layer.

Second, step (C) included after step (C-1) step (C-2), wherein themetallized substrate having the first nickel alloy metal layer wascontacted for approximately 2.5 to 5 min with an acidic secondmetalizing composition (pH approximately 3.3 to 3.7; temperature 55° C.,current density approximately 1.5 A/dm²) comprising nickel sulfate,nickel chloride, and boric acid (Watts-Nickel composition). Thus, step(C-2) is an electrolytic deposition of nickel.

Afterwards, the metalized substrate with the second nickel metal layerwas rinsed with water.

Afterwards, the respective substrates were contacted in a step (C-3)with a third metalizing composition (acidic pH) in order to obtain ametalized substrate having a copper layer with a layer thickness of morethan 30 μm (contact time about 45 min, 32.5° C., 40 g/L copper ions).

Subsequently, further metallization steps were carried out to preparechromium deposition.

In a final metallization step (C-x), the respective substrates werecontacted with a further metalizing composition in order to obtain ametalized substrate having a chromium layer, the further metalizingcomposition comprising 15 g/L to 30 g/L trivalent chromium and boricacid (acidic pH, 25° C. to 60° C.).

Finally, the optical quality of the chromium layer was evaluated byanalyzing coverage and optical defects. As a result, no haze and noother optical defects were observed. In particular, the chromium layershowed a very homogeneous optical distribution.

For adhesion tests, the substrates obtained after contacting with thethird metalizing composition (i.e. plated with copper) were subjected toadhesion tests. Typically, the adhesion for ABS was above 1.0 N/mm andfor ABS-PC in a range from 0.5 to 0.8 N/mm.

Compared to comparative examples depositing copper in steps (C-1) and/or(C-2) instead of nickel as carried out in the example above, the methodof the present invention showed a significantly higher adhesion (atleast 10%) and in addition a reduced tendency to form blisters. This wasparticularly observed for substrates, wherein in step (C-2) a copperlayer was deposited by immersion plating.

Furthermore, compared to comparative examples utilizing permanganate ina respective etching composition (e.g. as described in WO 2018/095998A1), the method of the present invention includes basically asingle-step pre-treatment sequence, which significantly reduces the timefor the entire pre-treatment procedure because no contacting with acomposition comprising a reducing agent and/or no second contacting stepwith a second or further manganese species is needed.

As a result of the present invention, a significantly lower degradationof the acrylonitrile-styrene matrix of the substrate is obtained leadingto a much less aggressive etching result. This is significant. Ownexperiments with samples of lower manufacturing quality have shown thatthe etching result obtained with the method of the present invention issufficiently homogeneous and still leads to a very acceptable opticalquality. Surprisingly, in our own experiments even substrates ofsignificantly lower quality showed a very homogeneous metallizationbecause defects in the substrate were less pronounced during thepretreatment step compared to other known pre-treatment methods, inparticular including permanganate ions.

This benefit most preferably applies to polybutadiene-comprisingsubstrates as investigated in our own experiments.

1. A method for metallizing a non-metallic substrate, the methodcomprising the steps: (A) contacting the non-metallic substrate with apre-treatment composition such that a pre-treated substrate is obtained,wherein the pre-treatment composition comprises: (A-a) individualmanganese (II), (III), and (IV) species, (B) contacting the pre-treatedsubstrate with an activation composition such that an activatedsubstrate is obtained, and (C) contacting the activated substrate withone or more than one metalizing composition such that a metalizedsubstrate is obtained, with the proviso that in the pre-treatmentcomposition, the total concentration of manganese (IV) species is higherthan the combined concentration of manganese (II) and (III) species, anelectrical current is applied to the pre-treatment composition such thatmanganese (II) species are oxidized to manganese (III) species, and instep (A) contacting said substrate with manganese species is carried outin a single step.
 2. The method of claim 1, wherein in step (A) thepretreatment composition is substantially free of, permanganate ions. 3.The method of claim 1, wherein in the pretreatment composition manganese(III) species disproportionate to manganese species comprising manganese(IV) species.
 4. The method of claim 1, wherein the electrical currenthas an anodic current density in a range from 0.1 A/dm² to 20 A/dm². 5.The method of claim 1, wherein during step (A) or prior to step (B) thepre-treated substrate is not contacted with a composition comprising areducing agent capable to chemically reduce manganese dioxide.
 6. Themethod of claim 1, wherein during step (A) in the pre-treatmentcomposition the total amount of all manganese species is more than 5.0g/L, based on the total volume of the pre-treatment composition and theelement manganese.
 7. The method of claim 1, wherein the pre-treatmentcomposition additionally comprises (A-b) one, two or more than twoacids.
 8. The method of claim 7, wherein the pre-treatment compositioncomprises at least a combination of sulfuric acid and phosphoric acid,wherein the phosphoric acid has a higher concentration than the sulfuricacid.
 9. The method of claim 1, wherein the pre-treatment compositionhas an absorbance of more than 1.0, referenced to a wavelength of 400 nmand a path length of 1 cm.
 10. The method of claim 1, wherein thepre-treatment composition additionally comprises (A-c) one or more thanone species of additional transition metal ions different frommanganese.
 11. The method of claim 1, wherein the pre-treatmentcomposition has a density in a range from 1.50 g/cm³ to 1.90 g/cm³,referenced to a temperature of 25° C.
 12. The method of claim 1, whereinstep (C) comprises a contacting with at least one metalizing compositioncomprising nickel ions.
 13. The method of claim 1, wherein step (C)comprises step (C-1) contacting the activated substrate with a firstmetalizing composition for electroless plating to obtain a metalizedsubstrate having a first nickel/nickel alloy metal layer, wherein thefirst metalizing composition comprises nickel ions and a reducing agentfor nickel ions.
 14. The method of claim 13, wherein step (C) comprisesafter step (C-1) step (C-2) contacting the metalized substrate havingthe first nickel/nickel alloy metal layer with a second metalizingcomposition for electrolytic plating to obtain a metalized substratewith a second nickel/nickel alloy metal layer, wherein the secondmetalizing composition comprises nickel ions.
 15. A pre-treatmentcomposition comprising (A-a) Mn(II) ions, Mn(III) ions, and colloidalmanganese (IV) species, (A-b) one, two or more than two acids, (A-c)silver ions, wherein the pre-treatment composition has a density in arange from 1.50 g/cm³ to 1.90 g/cm³, referenced to a temperature of 25°C., and an absorbance in a range from 1.1 to 2.1, referenced to awavelength of 400 nm and a path length of 1 cm, with the proviso thatthe pre-treatment composition is substantially free of methane sulfonicacid, salts thereof, and chloride ions, is substantially free ofpermanganate ions.
 16. The method of claim 1, wherein in step (A) thepre-treatment composition comprises permanganate ions only up to a totalconcentration of 100 mg/L, based on the total volume of thepre-treatment composition.
 17. The method of claim 1, wherein duringstep (A) or prior to step (B) the pre-treated substrate is not contactedwith a composition comprising any reducing agent.
 18. The method ofclaim 1, wherein step (C) comprises a contacting with at least twodistinct metalizing compositions each comprising nickel ions.
 19. Themethod of claim 13, wherein step (C) comprises after step (C-1) step(C-2) contacting the metalized substrate having the first nickel/nickelalloy metal layer with a second metalizing composition for electrolyticplating to obtain a metalized substrate with a second nickel/nickelalloy metal layer, wherein the second metalizing composition comprisesnickel ions- and is substantially free of a reducing agent for nickelions.